Certain correspondence is considered to be privileged, because it can play an important role in the protection of your rights, including your human rights.
Correspondence, in case you are convicted, with state agencies, local governments or their officials, your criminal defence counsel or a representative who is an advocate, is considered to be privileged. It is prohibited to refuse to forward a prisoner's letters to state agencies, local governments and the officials thereof, to criminal defence counsels and representatives who are advocates and consular officers of prisoner's country of nationality.
Correspondence, in case you are in custody, with criminal defence counsel, a representative who is an advocate, the Chancellor of Justice, a prosecutor, a court and the Ministry of Justice, is considered to be privileged. It is prohibited to examine the contents of prisoners' letters and telephone messages to a criminal defence counsel, representative who is an advocate, prosecutor, court, the Chancellor of Justice or the Ministry of Justice.
Any kind of interference with privileged correspondence requires very serious justification, which means that it should only be monitored in exceptional cases.
Read more about the types of privileged correspondence: